Poverty, Income, and Unemployment as Determinants of Life Expectancy: Empirical Evidence from Panel Data of Thirteen Malaysian States

Background: The primary indicator of public health, which all nations aim to prolong, is life expectancy at birth. Uncovering its socioeconomic determinants is key to extending life expectancy. This study examined the determinants of life expectancy in Malaysia. Methods: This observational study employs secondary data from various official sources of 12 states and one federal territory in Malaysia (2002–2014). Panel data of 78 observations (13 cross-sections at six points in time) were used in multivariate, fixed-effect, regressions to estimate the effects of socioeconomic variables on life expectancy at birth for male, female and both-gender. Results: Poverty and income significantly determine female, male, and total life expectancies. Unemployment significantly determines female and total life expectancies, but not male. Income inequality and public spending on health (as a percentage of total health spending) do not significantly determine life expectancy. The coefficients of the multivariate regressions suggest that a 1% reduction in poverty, 1% reduction in unemployment, and around USD 23.20 increase in household monthly income prolong total life expectancy at birth by 17.9, 72.0, and 16.3 d, respectively. The magnitudes of the effects of the socioeconomic variables on life expectancy vary somewhat by gender. Conclusion: Life expectancy in Malaysia is higher than the world average and higher than that in some developing countries in the region. However, it is far lower than the advanced world. Reducing poverty and unemployment and increasing income are three effective channels to enhance longevity.


Introduction
One of the most important indicators used as a measure of health status is life expectancy at birth. The highest worldwide life expectancy at birth is reported in Hong Kong (84.27 yr, in 2015; Fig. 1) (1). Life expectancy worldwide seems to be increasing rapidly, with recent re-search projecting that life expectancy at birth would reach 90 yr in South Korea by 2030 (2). In Malaysia, life expectancy has improved significantly over the last few decades, from 70. yr in 1990 to 74.87 yr in 2015 (Fig. 1). The latest available statistics (from 2015) show that Malay-sia has higher life expectancy than the world average (71.66 yr), as well as higher life expectancy than some developing countries in the region, such as Indonesia (69.07 yr). However, Malaysian life expectancy still trails that of advanced countries, including Malaysia's closest neighbor, Sin-gapore (82.59 yr) (1). Comparison of Malaysia with other countries shows that although Malaysia has achieved relatively good life expectancy, it still has a long journey ahead to approach the health status of the advanced world (1). Socioeconomic variables explain a large portion of variation in life expectancy (3)(4)(5). Factors such as poverty (3,4,6), income (7)(8)(9)(10)(11)(12), unemployment (13)(14)(15)(16), and income inequality (10,17) have all been found to predict variations in life expectancy in several studies of regions, nations, and economic clusters. However, the results of these studies have not always been consistent (17), suggesting that the socioeconomic determinants of life expectancy vary across regions, nations, and level of economic development. Thus, each country might have its own set of determinants of life expectancy (16).
In the Malaysian context, the commercialization of health care influences the health status of the Malaysian population, especially the poor (18). The share of public health spending as a percentage of total health spending dropped from about 90% before the late 1980s to a steady level around 55% in the late 1990s and thereafter (18,19

Statistical analysis
Bivariate associations between variables were initially assessed using Pearson correlation tests. Next, we performed three multivariate regressions to examine the adjusted determinants of life expectancy for females, males, and both genders.
Significance was set at the 5% level to accept or reject the null hypothesis. All regressions were cross-section, fixed-effect models since the Wald test supported fixed effects and the results of the Hausman test revealed no strong evidence for random effects. We found no evidence for using two-way, fixed-effect models because time dummies were not significant. We detected some heteroscedasticity, so for all regressions, we used standard errors and variance consistent with White heteroscedasticity. Notably, the 78 observations suffice for the above-described analyses, since the five independent variables with 12 dummies representing the state-based fixedeffects leave sufficient degrees of freedom for the residuals, which is good enough to obtain robust estimates. Some previous studies have used less than half this number of observations (16,25). Statistical analyses were performed using EViews 9 (IHS Global Inc., Irvine, CA, USA). This study was approved by the University of Malaya Research Ethics Committee (Reference No: UM.TNC2/UMREC -164).     where D is the unit change in the independent variable, β is the respective coefficient of the independent variable (As presented in Table 3), and 365 is the number of days of a single year. We used days instead of years for clearer comparisons of the magnitudes across variables and genders. b The initial unit of measurement for income in the regressions (Table 3) is thousand; however, for better illustration of the magnitudes, we used MYR 100 change in income in this

Increasing income, extending longevity
According to the results of this study, an increase of MRY 2200 (around USD 512) in monthly household income would add approximately one extra year to overall life expectancy across the country. Improving income is an effective method to prolong life expectancy in Malaysia, especially in states with relatively low household incomes and accordingly lower life expectancies (Fig. 2 A-B).
The results accord with most of the literature found positive effects of income on life expectancy (7)(8)(9)(10)(11)(12). In fact, income affects health-and thus life expectancy-via various channels. Higher-income reflects better social status, strongly linked to better physical and mental health (10,17,26,27). Much evidence documents that increasing income also improves access to health care (28,29). People with higher income adopt more-healthy lifestyles (30,31).

Towards "zero" poverty and a healthier nation
Poverty is the root of many diseases and causes of mortality; reductions in poverty levels have been widely linked to better health outcomes (25,32,33). Moreover, and in line with the results of this study, poverty has a significant, negative effect on life expectancy (3,4,6). Over the last decade, the prevalence of poverty in Malaysia was reduced from 6% in 2002 to 0.6% in 2014. The results of this study suggest that poverty eradication associates with better public health outcomes, higher life expectancy. The latest available statistics (2014) showed that the incidence of poverty reached zero in one Malaysian state (Johor; Fig. 2-C). However, poverty remains a minor problem in other states. The highest incidence of poverty (in 2014) was reported in the states of Kelantan and Terengganu (0.9%). Therefore, life expectancy could be improved by achieving "zero" poverty in all states; according to our results, eliminating the remaining 0.6% of Malaysian poverty would prolong life expectancy by about 10.7 d.

More employed women, longer life expectancies
Unemployment evidently worsens health status, thus increasing mortality and undermining life expectancy (13)(14)(15)(16). Moreover, the negative effect of unemployment is stronger on women's health than men's (15). As for life expectancy in Malaysia, our results confirm that unemployment negatively affects female life expectancy, but not male. At a national level, Malaysian unemployment has held nearly steady around 3% over the last decade (1). Although this level of unemployment is deemed healthy from an economic perspective, it would not seem to optimize national life expectancy. A further reduction in the unemployment rate from 3% to about 0.9% (as in the state of Melaka in 2014, Fig. 2-D) would extend female life expectancy by about half a year and total life expectancy by approximately five months. However, the economic side effects (increased inflation) of such a reduction in unemployment should also be considered (34).

The hidden effect of inequality
The effect of inequality on health remains controversial in the literature. Inequality had negative effects on life expectancy (10,17). Oher studies, however, have found no evidence for such an effect (35)(36)(37). The insignificant effects of inequality on health found by several studies could be attributed to indirect effects of inequality on health through other variables (mediators) (17). For instance, inequality increases poverty (38), and poverty leads to lower life expectancy; inequality thus may reduce life expectancy by increasing poverty. Moreover, inequality is well established to undermine income (39); inequality thus indirectly reduces life expectancy by reducing income.

Which sector spends on health care is irrelevant
Public sector health spending comprised more than 90% of overall Malaysian health spending until the late 1980s. Later, a new policy was implemented that aimed to partially commercialize the health care system, decreasing public share of health spending to about 55% in the late 1990s and thereafter (18,19). Our multivariate analyses revealed that the contribution of the public sector to health spending has no significant effects on life expectancy. Alternatively, the level of commercialization in the health sector has no effects on life expectancy.

Limitations
Due to limited data availability, about 12.2% of the Malaysian population were not included in this study. Regression estimates might have varied slightly if missing data were available and included. However, the results of this study remain valid and generalizable, since the employed sam-ple represents a very large fraction (87.8%) of the Malaysian population.

Conclusion
Malaysia has achieved relatively high health status, reflected by a life expectancy that exceeds the world average and some countries in the region. Nonetheless, life expectancy in Malaysia remains shorter than the advanced world. Eradication of poverty and improvements in female employment and household income are the factors driven life expectancy higher over the last decade. To approach better health status in Malaysia, the results of this study suggest poverty completely eliminated, while unemployment rates should be reduced as much as economically possible. Moreover, higher household income would also enhance national health in Malaysia.

Ethical considerations
Ethical issues (Including plagiarism, informed consent, misconduct, data fabrication and/or falsification, double publication and/or submission, redundancy, etc.) have been completely observed by the authors.